Forum Discussion
New MemberCyclone V HPS SPI Master: Formula for calculating Tsu(min)/Th(min) from rx_sample_dly and spi_m_clk
Hello,
For the HPS SPI Master on the Cyclone V SoC, verify that the SPI read waveform and register settings are correct.
To do this, calculate the MISO setup time and hold time under the operating conditions.
Current settings: rx_sample_dly = 1, spi_m_clk = 200 MHz
[Background]
The Cyclone V Device Datasheet and the Hard Processor System Technical Reference Manual do not contain a formula for determining Tsu (min) from rx_sample_dly and spi_m_clk.
In the datasheet, Tsu = 8.35 ns (min) is only shown as a characteristic value under the condition "rx_sample_dly = 1, spi_m_clk = 120 MHz" (Note 69).
Also, Th = 1 ns (min) has no note indicating its relationship with rx_sample_dly and spi_m_clk.
• [Reference] Cyclone V Device Datasheet → "SPI Timing Characteristics"
On the other hand, the datasheet for a newer generation device (such as the Agilex 3) equipped with the same SPI controller has the following expression:
• Tsu(min) = 5.0 − (rx_sample_dly × Tspi_ref_clk) [ns]
• Th(min) = 1.3 + (rx_sample_dly × Tspi_ref_clk) [ns]
• [Reference] Agilex 3 FPGAs and SoCs Device Data Sheet → "HPS SPI Timing Characteristics"
[What I want to know]
1. For the HPS SPI Master of the Cyclone V SoC, is there a formula to calculate Tsu (min) from rx_sample_dly and spi_m_clk periods like Agilex 3? If so, please tell me the formula and constant term.
2. Similarly, is there a formula to calculate Th (min) from rx_sample_dly and spi_m_clk periods? Also, please tell me under which condition (rx_sample_dly, spi_m_clk) Th = 1 ns (min) in the data sheet is the value.
3. If there is no official formula, is it correct to apply the same shape as Agilex3 (constant ̇ rx_sample_dly × T) to Cyclone V? If so, please tell me the constant to use. Also, I would like to know if the constant is based on rx_sample_dly = 0, and if 8.35 ns in the data sheet already includes 1 stage of rx_sample_dly.
4. Please tell me Tsu (min) and Th (min) under the current condition (rx_sample_dly = 1, spi_m_clk = 200 MHz).
Thank you for your support.
2 Replies
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Thank you very much.
tehjingy_AlteraRegular Contributor
Hi
Q1 & Q2 — Does the Cyclone V datasheet provide a Tsu/Th formula?
No — the Cyclone V datasheet does not publish a general formula analogous to Agilex 3's expressions.
Base on the foot note the operating point are (rx_sample_dly = 1, spi_m_clk = 120 MHz) for the Cyclone V.
Q3 — Can the Agilex 3 formula be applied to Cyclone V?
No - The formula used in the Agilex3 is not applicable to the Cyclone V. The formula is device specific.
Q4 — Tsu(min) and Th(min) at rx_sample_dly = 1, spi_m_clk = 200 MHz?
Since there is no formula in calculating the TSU min and Th min, the way moving forward is to "train" the bus with a coding loop.
By setting the rx_sample_dly as 1, check if there are any data errors in the bus, and increasing the value at a increment of 1 until there are no error seen.
